Lightweight vault cover

ABSTRACT

Disclosed is a cover for a utility vault and a method for making such covers. The cover is formed from fiberglass reinforcement layers and a polymer mix matrix. The reinforcement layers include a bottom reinforcement layer, one or more edge reinforcement layers, and a top reinforcement layer. A first portion of the edge reinforcement layer overlaps a portion of the bottom reinforcement layer and a second portion of the edge reinforcement layer overlaps a portion of the top reinforcement layer. The reinforcement layers are formed from fiberglass fabric and may include fiberglass layers whose fibers are oriented quadraxially. The polymer mix impregnates the fabric layers and forms the bulk of the cover. The polymer matrix bonds the reinforcement layers so that forces applied across the top and bottom layers are communicated to the edge reinforcement layer. The polymer matrix includes a thermoset polymer resin and an expanded glass bead filler.

This application is a divisional of U.S. patent application Ser. No.16/290,486 filed Mar. 1, 2019, which claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 62/637,253, filed on Mar.1, 2018. The disclosures of each application is incorporated herein byreference.

BACKGROUND Field

The present disclosure relates to covers for utility vaults, trenches,and other in-ground openings and to methods for forming such covers.More particularly, the present disclosure relates to lightweight vaultcovers formed from a glass bead filled polymer concrete with fiberglassreinforcements and methods for forming such covers.

Description of the Related Art

Equipment for utilities, such as transformers, switches, control panels,and valves are often housed in vaults located underground. Such vaultsinclude an opening at the top to allow workers to access the equipment,either by reaching down through the opening, or for larger vaults,allowing workers to descend into the vault. The opening must be coveredto protect the equipment from weather and from unauthorized access.Vault covers are generally shaped to conform to a collar formed at thetop of the vault surrounding the opening. The cover fits into the collarand may be secured to the top of the vault by bolts. The cover issupported at its edges by the collar.

The cover of many vaults lies at ground level to provide a continuoussurface with the surrounding area. For example, a vault may be locatedbelow a pedestrian sidewalk. To avoid a tripping hazard, the vault coverneeds to be substantially flush with the surrounding sidewalk. Likewise,the cover of a vault located below a roadway must be substantiallyco-planar with the road to allow vehicles to pass. Because the cover isflush with the ground, it may be subject to heavy loads, such as when avehicle drives over the cover. To avoid damage, vault covers need to bestrong enough to withstand the maximum load expected for a particularsituation.

Known vault covers are typically made from moldable materials, such asconcrete. The concrete forming known vault covers is a mixture of acement and a mineral aggregate. The cement may be a thermoset polymerresin. The aggregate may be a combination of mineral materials withcomponents of various sizes from sand to small gravel. Because concretemay have low tensile strength, known covers may include strengtheningmembers, such as rebar, to withstand tensile loads.

Vault covers need to be removed from time to time to allow workers toaccess equipment in the vault. Typically, vault covers include a handleor lifting pin that can be grasped by the worker. A single worker may beable to lift a small cover without tools. For larger covers, such asthose that allow a worker to bodily enter the vault, the weight of thecover may prevent the worker from lifting it himself. The worker mayneed to bring a tool, such as a cover lifter or heavy equipment such asa backhoe, to open the vault. This adds cost and complexity to the taskof servicing equipment in the vault. If lighter materials are used toform the cover, such as by using thinner rebar, or using less of theaggregate, the strength of the cover may be reduced.

Thus, there is a need for a vault cover that provides high strength toresist loads, while at the same time having less weight than knowncovers to facilitate convenient access to the vault.

SUMMARY

The present disclosure relates to apparatuses and methods to addressthese difficulties.

According to one embodiment, there is a vault cover comprising a polymermix matrix, a top reinforcement, a bottom reinforcement, and one or moreedge reinforcements. The reinforcements comprise layers of fiberglassfabric. According to one embodiment, the fiberglass fabric is formedfrom fibers arranged quadraxially. The matrix comprises a thermosetpolymer cement and an expanded glass bead filler. The matrix infiltratesand binds with the reinforcements. The edge reinforcement sheet overlapsthe edges of the top reinforcement and the bottom reinforcement. Whenthe thermoset polymer hardens it binds the edge reinforcement to the topand bottom reinforcements.

According to another embodiment, a method for forming a vault cover isprovided comprising the steps of providing a mold cavity, placing a topreinforcement layer along a bottom surface of the mold cavity, placingan edge reinforcement along at least one edge of the mold cavity,wherein a first portion of the edge reinforcement overlaps a portion ofthe top reinforcement and second portion of the edge reinforcementextends out of the mold cavity, substantially filling a space within theedge reinforcement and above the top reinforcement with one or morecomponents of a matrix material, placing a bottom reinforcement layer ontop of the at least one component of the matrix material, and foldingthe second portion of the edge reinforcement over the bottomreinforcement layer. In one aspect the at least one component of thematrix material is a filler and the method further comprises the step ofintroducing a second component of the matrix material into the moldcavity, wherein the second component is a polymer resin that infiltratesthe interstitial spaces of the filler material and the top, edge, andbottom reinforcements. The step of introducing may be performed usinginjection molding, such as by placing a top lid over the mold cavity,applying a negative pressing to the cavity through an outlet port, andinjecting the resin into the cavity via an inlet port. The resin maycomprise one or more of an unsaturated polyester resin, a methacrylate,a vinyl ester, and an epoxy.

According to another aspect the one or more components of the matrixmaterial comprise a mixture of a polymer cement and a filler, and thestep of substantially filling comprises infiltrating the mixture intothe top and edge reinforcements with a first portion of the mixture and,following the step of folding, the method further comprises pouring asecond portion of the mixture into the mold cavity and infiltrating themixture into the bottom reinforcement.

One or more of the top reinforcement layer, the bottom reinforcementlayer, and the edge reinforcement layer may be formed by a fiberglassfabric. The fabric may comprise a quadraxial fabric. The one or morecomponents of the matrix material may comprise one or more of glassbeads, expanded glass beads, limestone aggregate, silica sand, choppedfiberglass fibers, polymer fibers, metallic fibers, fly ash, expandedceramic spheres and ceramic particles.

The method may include forming features on one or more surfaces of themold cavity, wherein the features form one of more of a slot, a bolthole, a textured surface, and an indicia. According to one aspect of themethod an edge of the vault cover formed by the disclosed method has acurvilinear shape and the method further comprises the steps of notchingthe edge reinforcement and fitting the notched edge reinforcement intothe mold cavity to conform to the curvilinear shape.

According to another embodiment of the disclosure, there is provided avault cover comprising a bottom reinforcement layer, at least one edgereinforcement layer, a top reinforcement layer, and a matrix, wherein afirst portion of the edge reinforcement layer overlaps a portion of thetop reinforcement layer, and a second portion of the edge reinforcementlayer overlaps a portion of the bottom reinforcement layer and whereinthe overlapping portions are bonded with one another by the matrix.

One or more of the top reinforcement layer, the bottom reinforcementlayer and the edge reinforcement layer may be formed by a fiberglassfabric. The fiberglass fabric may be a quadraxial fabric. The matrix maycomprise a filler and one or more of an unsaturated polyester resin, amethacrylate, a vinyl ester, and an epoxy. The filler may comprise oneor more of glass beads, expanded glass beads, limestone aggregate,silica sand, chopped fiberglass fibers, polymer fibers, metallic fibers,fly ash, expanded ceramic spheres and ceramic particles

According to one aspect, the vault cover is adapted to cover a utilityvault, a trench, or an opening in a road surface. The vault cover mayinclude lifting pins, fastener holes, a textured surface, and indicia.One or more of a RFID device, an electronic sensor, and an inductioncoil may be embedded in the matrix of the vault cover. According to oneaspect, when tested according to ANSI SCTE 77 Tier 22, the load atfailure of the vault cover is greater than 33,000 pounds.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a vault including a cover according toan embodiment of the disclosure;

FIGS. 2a-d are cross sections of a mold cavity showing steps for forminga cover according to an embodiment of the disclosure;

FIG. 3 shows a cross sectional view of a portion of a cover formed bythe steps of FIGS. 2a -d;

FIG. 4a is a cross section showing a prior art cover installed on avault without a load applied;

FIG. 4b shows the prior art cover of FIG. 4a with a load applied to itstop surface;

FIG. 5 is a cross section of a cover according to an embodiment of thedisclosure installed on a vault with a load applied to its top surface;

FIG. 6a is a perspective view of a cover according to an alternativeembodiment of the disclosure;

FIG. 6b is a plane view of an edge reinforcement used to form the coverof FIG. 6a ; and

FIGS. 7a-c are cross sections of a mold cavity showing steps for forminga cover according to a further embodiment of the disclosure.

DETAILED DESCRIPTION

FIG. 1 shows an underground utility vault 6. The vault 6 includes avault chamber 2, a collar 4, and a cover 1. The chamber 2 is sized tohold equipment, such as electrical connections, switches, transformers,valves, meters, and the like. Collar 4 is positioned at the top of thechamber 2. Cover 1 fits within collar 4 and rests against a shoulderalong the inner edge of collar 4. Vault 6 is designed to be installedbelow ground, for example, beneath a roadway, a sidewalk, or a lawn withthe cover 1 flush with the ground surface. Cover 1 may include one ormore lifting pins 8 located within slots 7. Bolts may be provided inbolt holes 9 to secure cover 1 onto collar 4. Bolts may have a securityfeature such as a head requiring a specialized tool, for example, apentagonal shape, to discourage unauthorized persons from tampering withthe vault or its contents. Cover 1 may have a textured top surface toincrease friction and reduce the chance that a person may slip whenwalking across the cover. Cover 1 may also include indicia, for example,“TRAFFIC SIGNAL” or “WATER VALVE” to indicate the type of contentswithin the vault 6.

According to another embodiment, instead of covering a vault, cover 1forms a trench cover for removably covering a trench, such as a trenchfor holding below ground utility services. According to this embodiment,the width of cover 1 is such that it spans the width of the trench. Sucha cover may be elongated to extend along the whole length of the trenchor multiple covers covering portions of the trench may be used dependingon the length of the trench. According to one aspect, cover 1 rests onshoulders formed along the top edges of the trench so that the topsurface of the cover is flush with the surrounding ground surface.

According to another embodiment, cover 1 forms a road plate for coveringa hole in a road bed, for example, while repair work is done onstructures beneath the surface of a road. According to one aspect, theroad plate is provided with beveled edges so that, when it is positionedon the surface of a road, vehicles can easily roll onto and off of theroad plate.

FIGS. 2a-2d are cross sectional views of a portion of a mold 10illustrating steps to form cover 1. A variety of cover shapes and sizescan be formed by varying the size and shape of the cavity of mold 10. Asshown in FIG. 2a , a first portion 16 of a polymer mix is poured intothe mold cavity. A top reinforcement 14 is placed into the mold and iswetted by the polymer mix. According to one alternative embodiment, thetop reinforcement is placed into the mold first and the polymer mix ispoured over the reinforcement. The top reinforcement may be a fiberglassfabric, such as 18 oz. woven roving. Top reinforcement extends parallelto the bottom surface of the mold cavity and covers substantially thewhole of the bottom surface of the mold cavity.

According to one embodiment, features of cover 1 such as slots 7, boltholes 9, indicia, and/or texturing on the finished part are formed bythe shape and texture of the bottom surface of the cavity of mold 10.Where the shape of the bottom surface of the mold cavity extendssubstantially upward from the bottom of the mold, for example, to formslots 7 and bolt holes 9, top reinforcement 14 is cut to fit aroundthese features. In addition, structures to be embedded in the vaultcover 1, such as lifting pins 8, may be placed in the mold 10 prior topouring in polymer mix 16.

Edge reinforcement 12 is placed into the cavity 10 as shown in FIG. 2a .A portion 13 of the edge reinforcement 12 overlaps the top reinforcement14. Another portion 15 of the edge reinforcement 12 extends out of themold cavity and rests on the side of the mold. The polymer mix 16 wetsoverlapping portion 13. When the polymer mix solidifies, it will createa bond between overlapping portion 13 and top reinforcement 14.

According to alternative embodiment, edge reinforcement 12 is placed inthe mold first, with a first portion 13 lying on the bottom surface ofthe mold cavity and a second portion 15 extending out of the cavity 10.Top reinforcement 14 is then laid into the bottom of the mold cavitywith the edges of the top reinforcement layer lying on top of the firstportion 13 of the edge reinforcement. The first portion 16 of thepolymer mix is then poured into the mold cavity. This embodiment differsfrom what is shown in FIG. 2a in that the top reinforcement 14 overliesthe first portion 13 of the edge reinforcement 12.

According to one embodiment, edge reinforcement 12 is a fiberglassfabric, such as a woven roving or a biaxial or triaxial fiberglassfabric. According to a preferred embodiment, reinforcement 12 is aquadraxial fiberglass fabric with fibers aligned in separate layersoffset from one another by 0°, 90°, −45°, +45°. The layers may bestitched to one another using, for example, polyester stitching at 1inch intervals. According to a preferred embodiment, the fiberglassfabric is a 48 oz. per square yard quadraxial fiberglass fabricmanufactured by Flotex™ and sold under part number E-LHXF-4800. Fabricsmade by other manufacturers can be used and other weights of quadraxialfabrics can also be used including 36 oz. per square yard fabric. Suchfabrics have an open structure, allowing liquids, such as the polymermix, to readily infiltrate between the fiberglass fibers and wet thefibers. According to one embodiment, the surface of the fibers ischemically or mechanically treated to be readily wetted by the polymermix and to securely bond with the polymer mix once the polymer mixhardens.

As shown in FIG. 2b , a second portion 20 of polymer mix is poured intothe cavity of mold 10. A bottom reinforcement 18 is placed into the moldcavity on top of the second portion of 20 of the polymer mix. Bottomreinforcement may be a fiberglass fabric. According to a preferredembodiment, bottom reinforcement 18 and top reinforcement 14 are formedfrom the same quadraxial fiberglass fabric that forms the edgereinforcement 12.

As shown in FIG. 2c , portion 15 of reinforcement 12 is folded overbottom reinforcement 18. In an alternative embodiment to what is shownin FIG. 2c , portions 15 are folded into the mold cavity before thebottom reinforcement 18 is placed into the cavity. This alternativeembodiment differs from what is shown in FIG. 2c in that the bottomlayer 18 overlies the second portions 15 of the edge reinforcement.

As shown in FIG. 2d , a third portion 24 of polymer mix is poured intothe mold cavity 10 to wet portion 15 and reinforcement 18 and to fillthe cavity. When the polymer mix hardens it will form a bond betweenbottom reinforcement 18 and edge reinforcement 12 and between the topreinforcement 14 and edge reinforcement 12. As shown in FIG. 2d , a topportion of mold 22 may be closed over the mold 10. Force may be appliedto the top 22 by a mechanical, pneumatic, or hydraulic clampingmechanism or by placing weights on the top 22 to apply increasedhydrostatic pressure to the polymer mix, driving the mix to infiltratethe fiberglass reinforcements 12, 14, 18 and helping to drive airbubbles out of the matrix. According to another embodiment, instead ofclosing mold 10, as shown in FIG. 2d , the mold is left open and thepolymer mix is allowed to set with the surface of the mix exposed.

According to one embodiment, the polymer mix includes a thermosetpolymer such as a polyester resin. The resin includes a hardenercomponent that is mixed with the resin prior to pouring the mix into themold cavity to initiate a chemical reaction to cause the mix tosolidify. According to one embodiment, the resin is an unsaturatedpolyester resin sold as Polynt™ 768-6871 by Polynt SpA. This resin is alow-viscosity (100 cps) resin, promoted using cobalt octuate anddimethylaniline and cured using a methyl ethyl ketone peroxide (mekp).According to other embodiments the polymer resin is an unsaturatedpolyester promoted solely with anilines and cured using benzoyl peroxide(bpo). According to further embodiments, the resin is a methacrylate, avinyl ester, or an epoxy. Such resins can be cured using theabove-mentioned metal salt/peroxide and/or aniline/peroxide systemsalready mentioned, but also heat-activated and UV curing systems.

According to one embodiment, a filler is added to the polymer mix suchas limestone aggregate, silica sand, chopped fiberglass fibers, polymerfibers, metallic fibers, fly ash, and/or combinations thereof. Accordingto a preferred embodiment, the filler comprises glass beads instead of,or in addition to other fillers such as limestone aggregate. To reducethe weight of the finished cover 1, the glass beads may be expandedusing techniques known to those of skill in the field of the invention.The glass beads may be formed from recycled materials. According to oneembodiment, the filler is entirely expanded glass beads and comprisesfrom 20% to 80% by weight of the polymer mix. According to a morepreferred embodiment, the glass beads comprise between 40% and 70% byweight of the polymer mix. According to a most preferred embodiment, theglass beads comprise 55% by weight of the polymer mix. According to apreferred embodiment, the glass bead filler is manufactured by DennertPoraver GmbH with a particle size from 0.04 mm to 8.0 mm and has anapparent density from 20 to 60 lb/cubic foot, depending on the particlesize. According to a further embodiment, instead of expanded glassbeads, the filler comprises other lightweight materials such as expandedceramic spheres or particles. Using expended glass beads results in areduction in weight to the cover 1 compared with covers made usingmineral aggregates.

FIG. 3 shows a detailed view of the edge of cover 1 after the polymermix has hardened into a continuous concrete mass 26 and the cover hasbeen removed from the mold and oriented upright. Top reinforcement 14lies within the mass 26 below the top surface 28. The hardened polymermix, which has infiltrated reinforcements 12, 14 and 18 bondsoverlapping portions 13 and 15 of the edge reinforcement 12 with the topreinforcement 14 and bottom reinforcement 18, respectively.

Construction of a cover according to an embodiment of the disclosureresults in a light weight structure with a significant increase instrength. As an example, in one investigation three covers withidentical polymer mix material including a glass bead filler wereproduced with different reinforcement strategies. The baseline cover(Part #1) was made with a traditional fiberglass strategy of a “faceglass” and a “back glass” with each glass being 18 oz biaxialconstruction. No edge reinforcing layer was provided. Part #2 was madeusing the 18 oz biaxial glass construction, but adding 18 oz glass“wrapped” around the part edges. Part #3 was made replacing the 18 oz“back glass” and “wrap glass” with quadraxial 36 oz glass arranged asshown in FIG. 3. Each part was destructively tested (per ANSI SCTE 77Tier 22 requirements) with the following results:

TABLE 1 Load at Failure Part #1 16,200 Lbs Part #2 32,560 Lbs Part #351,970 Lbs

As shown in Table 1, adding a fiberglass reinforcement to the edge ofthe cover in Part #2 has the unexpected effect of significantlyincreasing strength compared with a cover formed without edgereinforcement, Part #1 while adding very little additional weight. Inaddition, by providing a quadraxial fiberglass fabric as an edgereinforcement, Part #3, strength is increased still further.

According to further embodiments of the disclosure structures areembedded in the polymer matrix during assembly of cover 1. For example,RFID circuitry can be provided in the cover to enable workers toidentify the location and contents of a vault using an electronicsensor. Cover 1 may include circuitry that interfaces with a meterhoused in the vault to allow workers to remotely monitor the quantity ofelectricity, water, or gas used by a utility customer. Induction coilsfor monitoring the location and speed of vehicles in the vicinity of avault can be provided to facilitate operation of traffic controldevices, e.g., stoplights.

FIGS. 4a and 4b illustrate a known vault cover 100. As shown in FIG. 4a, cover 100 includes a bottom reinforcement 102 embedded in a moldedpolymer matrix 104. The reinforcement 102 may be a fiberglass fabricinfiltrated with the polymer matrix 104. Cover 100 may be installedwithin a collar 4 of a vault 6, such as the one shown in FIG. 1. FIG. 4bshows cover 100 with a force F applied to the top of the cover. Such aforce may be the result of a vehicle or other heavy object on top of thecover. Because cover 100 is supported along its edges by collar 4,downward force will cause cover 100 to flex with the bottom surface intension. Because reinforcement 102 impregnated with the solidifiedpolymer is stiff, it tends to pull away from the bottom of the cover 100and delaminate. As a result, the cover 100 loses strength and maycollapse, potentially causing damage to the vault and any equipmentresident in the vault.

FIG. 5 shows cover 1 according to the present disclosure installedwithin the collar 4 of a vault with downward force F applied. Here,because the edge reinforcements 12 are bonded with the bottomreinforcement 18 at each edge of the cover, the bottom reinforcementdoes not delaminate from the cover. Instead, tensile forces along thebottom surface 30 of the cover 1 are communicated to the edgereinforcements and then through the thickness of the cover to the topreinforcement 14. In addition, because the edge reinforcements 12 areformed from a quadraxial fabric with fibers aligned in differentdirections (i.e., at 0°, 90°, −45°, +45°), any tensile force applied tothe edge reinforcements will be in a direction no more than 22.5° fromthe axis of fibers in at least one layer. Likewise, in embodiments wherebottom reinforcement 18 is also formed from a quadraxial fiberglassfabric, tensile forces along the bottom surface 30 of the cover willlikewise be substantially aligned (i.e., within 22.5°) with at least onelayer of the fibers. This alignment allows tensile forces to becommunicated from the bottom surface 30 to the edges and through thethickness of the cover 1. According to some embodiments, thisarrangement of reinforcements allows covers made from lightweightconcrete to have sufficient strength without embedded rebars.

FIG. 6a shows a further embodiment of the disclosure. Cover 1 is round,making it suitable for application such as covering a manhole. Such acover may be formed in a manner similar to the embodiments disclosedabove. FIG. 6b shows an edge reinforcement 12 used to form theembodiment of FIG. 6a . In this embodiment, a single edge reinforcementextends around the circumference of the mold 10. Reinforcement 12 isnotched along each edge to allow the overlapping portions 13 and 15,discussed with respect to FIGS. 2a-d and FIG. 3, to fit within a roundmold cavity without bunching. According to other embodiments, bynotching the edge reinforcement, covers with a variety of curvilinearshapes may be formed with a continuous edge reinforcement.

FIGS. 7a-d show a method of forming a vault cover according to a furtherembodiment of the disclosure. In this embodiment, rather than mixing afiller, such as glass beads, with a polymer resin and pouring themixture into the mold, an injection molding process is used.

As shown in FIG. 7a , an injection mold 100 is provided with a moldcavity 102 shaped to form the vault cover. An edge reinforcement 112 isprovided along the edge of the cavity 102 with a first portion 113 laidalong the bottom surface of the cavity 102 and a second portion 115 laidover the edge of the mold 100. A top reinforcement 114 is placed alongthe bottom surface of the cavity 102 overlapping the first portion 113of the edge reinforcement 112. The reinforcements may be formed from thesame fiberglass materials are described in the previous embodiments.According to a preferred embodiment, the reinforcements are formed froma fiberglass material, such as 36 oz. pr square yard or 48 oz. persquare yard quadraxial fiberglass fabric. According to one aspect of theinvention, a breather layer (not shown) may be placed between thereinforcements 112 and 114 and the inside surface of the mold cavity102. The breather layer provides additional pathways for resin and airto flow through the mold during the injection molding process, as willbe described below.

As shown in FIG. 7b , filler material 116 is placed in the mold cavity102, filling the space inside the edge reinforcement 113 and above thetop reinforcement 114. The filler material may be the same material asdescribed in the previous embodiments. According to a preferredembodiment, the filler material 116 is expanded glass beads.

As shown in FIG. 7c , a bottom reinforcement is placed over the fillermaterial 116. Again, the bottom reinforcement may be the same fiberglassfabric as described in previous embodiments. The second portion 115 ofthe edge reinforcement is folded into the mold cavity and overlaps aportion of bottom reinforcement 118. A mold cover 106 is placed overmold cavity 102 and sealed. A breather layer (not shown) may be providedbetween the bottom reinforcement 118 and the cover 106. Outlet port 108on the mold cover 106 is connected with a vacuum system to provide anegative pressure to the interior of the mold. A source of injectionmolding resin is connected with mold inlet port 104. Resin is injectedinto the mold cavity via inlet port 104 while negative pressure isapplied to the outlet port 108. Resin infiltrates the reinforcements,the breather layers (if used), and the filler material 116 and fills theinterstitial spaces within the mold cavity. The resin is allowed toharden, thus bonding edge reinforcement 112 to the top and bottomreinforcements 114, 118 and forming a solid vault cover.

According to a further embodiment, the top, edge, and bottomreinforcements are pre-assembled, for example, by sewing or adhesivelyattaching portions of fabric with one another and the space inside theassembled fabric portions is filled with the filler material, e.g.,expanded glass beads. The preformed assembly is then placed in the moldcavity and injection molded, as described with respect to FIG. 7 c.

While illustrative embodiments of the disclosure have been described andillustrated above, it should be understood that these are exemplary ofthe disclosure and are not to be considered as limiting. Additions,deletions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the disclosure. Accordingly, thedisclosure is not to be considered as limited by the foregoingdescription.

We claim:
 1. A method for forming a vault cover comprising the steps of:providing a mold cavity; placing a top reinforcement layer along abottom surface of the mold cavity; placing an edge reinforcement alongat least one edge of the mold cavity, wherein a first portion of theedge reinforcement overlaps a portion of the top reinforcement andsecond portion of the edge reinforcement extends out of the mold cavity;substantially filling a space within the edge reinforcement and abovethe top reinforcement with one or more components of a matrix material;placing a bottom reinforcement layer on top of the at least onecomponent of the matrix material; and folding the second portion of theedge reinforcement over the bottom reinforcement layer.
 2. The method ofclaim 1, wherein the at least one component of the matrix material is afiller and further comprising the step of introducing a second componentof the matrix material into the mold cavity, wherein the secondcomponent is a polymer resin that infiltrates the interstitial spaces ofthe filler material and the top, edge, and bottom reinforcements.
 3. Themethod of claim 2, wherein the step of introducing is performed usinginjection molding.
 4. The method of claim 1, wherein the one or morecomponents of the matrix material comprise a mixture of a polymer cementand a filler, wherein the step of substantially filling comprisesinfiltrating the mixture into the top and edge reinforcements with afirst portion of the mixture and, following the step of folding, furthercomprises pouring a second portion of the mixture into the mold cavityand infiltrating the mixture into the bottom reinforcement.
 5. Themethod of claim 1, wherein one or more of the top reinforcement layer,the bottom reinforcement layer and the edge reinforcement layer are afiberglass fabric.
 6. The method of claim 5 wherein the fiberglassfabric comprises a quadraxial fabric.
 7. The method of claim 1, whereinthe one or more components of the matrix material comprise one or moreof glass beads, expanded glass beads, limestone aggregate, silica sand,chopped fiberglass fibers, polymer fibers, metallic fibers, fly ash,expanded ceramic spheres and ceramic particles.
 8. The method of claim3, further comprising the steps of: placing a top lid over the moldcavity; applying a negative pressing to the cavity through an outletport; and injecting the resin into the cavity via an inlet port.
 9. Themethod of claim 2, wherein the resin comprises one or more of anunsaturated polyester resin, a methacrylate, a vinyl ester, and anepoxy.
 10. The method of claim 1, wherein a feature is provided on aninterior surface of the mold cavity, wherein the feature forms one ofmore of a slot, a bolt hole, a textured surface, and an indicia.
 11. Themethod of claim 1, wherein an edge of the vault cover has a curvilinearshape, the method further comprising the steps of notching the edgereinforcement; and fitting the notched edge reinforcement into the moldcavity to conform to the curvilinear shape.
 12. The method of claim 1,further comprising embedding one or more of a RFID device, an electronicsensor, and an induction coil embedded in the matrix.